Lubricating oil



Patented Sept. 5, 1939 PATENT OFFICE LUBRICATING on.

Arthur B. Brown, Hammond, Ind., and Fred F. Diwoky, Chicago, 11]., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application March 3, 1938, Serial No. 193,771

3 Claims.

This invention relates to the extraction of mineral oils with admixtures of organic solvents.

Petroleum is essentially an admixture of hydrocarbons comprising several groups or homolo- 5 gous series of compounds such as Daraflins, hy-

droaromatics, aromatics, poly-methylenes, and various other series'in which the hydrogen to carbon ratio is even lower than in the above series. A large number of individual compounds of each series are present and have different boiling points, physical and chemical properties.

In the various types of crude petroleum commonly known as paraifinic base, naphthenic or asphalt base and mixed base oils, these various -l5.;series of hydrocarbons are present in difierent proportions. For example, in the paraflin base oils such as those from the Appalachian field,-

there is a relatively high proportion of paramnic hydrocarbons having a chain structure and a 20 high hydrogen to carbon ratio, whereas the Gulf Coastal oils have a high proportion of hydrocarbons with ring structures and a low hydrogen to carbon ratio, which are generally referred to as non-parafiinic or naphthenic constituents. The -mixed base oils such'as those from Oklahoma and the Mid-Continent areas are in general intermediate between these two extreme types.

In the normal refining of crude petroleum, the fractions of varying distillation ranges which are successively obtained by distillation of the oils partake of the general character of the crude; for example, lubricating oils derived from Appalachian crudes show paraflinic characteristics,

whereas the lubricating oils derived from Texas crude show naphthenic characteristics. The distillates from the mixed base crudes, such as those from the Mid-Continent area, show characteristics common to both the parafiinic and naphthenic oils. Similarly, the undistilled oils or re- A siduums have properties resembling the crude from which they are prepared. An important property of parafilnic lubricating oils is the low viscosity temperature coeflicient or the rate of change of viscosity with temperature. This 45 property makes them particularly suitable for treatment with fuming sulfuric acid, followed by neutralization and removal of harmful sulfuric acid derivatives.

An object of this invention is to provide an improved admixture of solvents for extracting the naphthenic or non-paraffinic constituents from mixed base mineral or lubricating oils and asphalt base oils so that the resulting oil will have improved viscosity characteristics and will contain a high proportion of paraflinic hydro- 1 carbons. These new solvents may be used for extracting lubricating oil distillates or residual lubricating oils.

Another object of our invention is to provide an improved admixture of solvents for extract- 15 ing these mineral lubricating oils in order to improve the color of the oil and at the same time remove the sludge forming or non-paraflinic constituents.

A further object is to provide a method for treating petroleum oils containing non-paraflinic constituents without the expense and nuisance of acid treatment, and without the loss of valuable petroleum constituents which accompanies the use of acid treating. A further object is to provide a lubricating oil with a minimum tendency toward sludge formation when exposed to oxidizing conditions.

A further object of our invention is to provide an admixture of solvents which maybe used in combination with a non-viscous, normally gas- .eous liquid hydrocarbon for extracting mineral oils containing paraflinic and non-paraflinic constituents.

T A particular object of our invention is to provide an admixture of solvents which can be used at ordinary temperatures to separate the oil into paraflinic and non-paraflinic constituents.

The expression viscosity index" as used herein refers specifically to the index defined by Dean and Davis in Chemical and Metallurgical Engineering, vol. 36 (1929), page 618. The viscosity index of a lubricating oil is an indication of its composition or type; i. e., whether it is a parailin 45 base or naphthene base oil. Paraffin base oils are arbitrarily assigned a viscosity index of 100, naphthene base oils are assigned a viscosity index of 0, and mixed base oils lie between these extremes. to obtain from mixed base lubricating oils or oils containing some non-paraflinic constituents a maximum yield of paramn type oils having a low true color (with a high viscosity index) without the nuisance or cost of acid treating and without 55 An object of the present invention is In accordance with one feature of this invention, we have discovered that each of the follow- 5 ing admixtures of solvents is particularly efiective for; use in the extraction of mineral oils: cresylic acid and chloraniline, cresylic acid and chlorophenol, phenol and chloraniline. In using any of these admixtures of solvents, we may use from about one to three volumes of the mixed solvent to one volume of oil; however, smaller or larger volumes of the mixed solvent may be used. The proportion of the two components that make up the solvent may vary from 85% of one component to 85% of the other. For example, the admixtures may be 15 to 85% cresylic aid and 85 to 15% chloraniline; or 15 to 85% cresylic acid and 85 to 15% chlorophenol. Without limiting the foregoing description of the ratio of components used to make up the solvent, the following examples of combined solvents may be used: 7

Per cent Cresylic acid; 40 to 60 Chloraniline 60 to 40 Cresylic acid 40 to 60 Chlorophenol '60 to 40 Phenol 15 to 60 Chloraniline 85 to 40 This invention is applicable to the treatment of any mineral oil such as the Pennsylvania, Mid-Continent and coastal oils but it is particularly applicable to the treatment of mixed base distillate or residual oils. Oils having a true color from 800 to 900 or above may be refined by our solvents to give rafllnates having true colors from 300 to 200 or less. For example, it may be used to improve the color and remove the naphthenic'or other non-paraflinic constituents from oils having a viscosity within the range of 200-3500 seconds Saybolt at 100-F. The solvents may also be used in the presence of nonviscous normally gaseous hydrocarbons such ashydrocarbons are generally referred to as dilu-' ents.

The process may be performed by mixing the mineral oil with one of the above admixtures of solvents and then heating the resulting mixture in order to dissolve the oil in the solvent. If desired, the mixture may be agitated during the heating. After the oil and solvent have been heated to the temperature where substantially complete miscibility is obtained, the solution is cooled until phase separation occurs. The tem-' perature at which miscibility is obtained is termed the miscibility temperature and the temperature at which phase'separation is obtained is termed the extraction temperature". Alternatively, the oil and solvent may be agitions will be found to this general rule. One feature of the present admixture of solvents resides in the fact that phase separation will occur at a relatively high temperature, for example, above about 70 F. Since phase separation will occur at relatively high temperatures, our process can be used very effectively without the aid of artificial cooling.

The upper layer or phase which consists mainly of the paraflinic fraction is referred to as the rafilnate and the compounds which are dissolved in the solvent in the lower phase are called the extract. Due to the solvent nature of the oil, some of the solvent will be found in the rafilnate fraction. The liquid phases may be separated from each other by decantation or other suitable means. After separating the two layers, they are heated in separate stills in order to distill oil the solvent. The thus recovered solvent is reused in the process. If desired, steam stripping may be used to assist in the removal of solvent from the oil. The raflinate which is produced by our process consists of hydrocarbons having a high viscosity index, excellent color and good sludge stability, and it is particularly suitable for lubricants.

.Generally, it is not necessary to give the rafflnate a further refining treatment in order to.

produce suitable lubricating oils, however, if desired, the raflinate may be given a further light refining treatment. The combination of solvents that ,we have discovered, however, have the unique property of imparting a very low true color to the ramnate.

As an example of the method of carrying out our process, one volume of dewaxed Mid-Continent S. A. E. distillate having a viscosity of about 126 seconds at 210 F., viscosity index of 59.4, true color of 1070 and a gravity of 20.7 A. P. I. was admixed with one and one-third volumes of solvent consisting of equal proportions of chloraniline and cresylic acid. The resulting admixture was then cooled to the extraction temperature, 72 F., where phase separation occurred. The admixture of solvents and dissolved non-parafllnic or naphthenic constituents separate to form the lower layer and the parafflnic oil or rafllnate forms the upper layer. The lower layer was withdrawn from the upper layer and the admixture of solvents removed from each fraction by distillation. The distilled solvents are reused in the extraction process. The amount of solvent retained in the raflinate fraction is relatively small and may be removed therefrom by distillation or by stripping with an inert gas or fluid such as carbon dioxide or steam. The raflinate may be given an additional extraction with the same admixture of solvents or one of the other admixtures herein disclosed.

tated at a temperature equal to or slightly above the extraction temperature until the oil and solvent become miscible. By permitting this mixture to stand, preferably with slight cooling, phase separation will take place. In most commercial extraction systems, the oil and solvent are brought into solution at about the extraction temperature. With most oils, the extraction temperature is usually 40 F. or more below the i miscibility temperature, however, some excep- Our solvents may be used in the counter-current extraction of oils as well as batch extractions.

The following table shows the properties hi the above raflinate obtained by the single extraction, and for, convenience the properties of the original oil are also shown to illustrate the improved results:

It is apparent from the abovedata'that the adv above example also was extracted with one and one-third. volumes of a solvent which consisted of equal proportions of cresylic acid and chlorophen01.v This extraction was carried out exactly as the above extraction and the following table shows the utility of this particular admixture of solvents:

G t Viscosity V t Pep [8V1 y 150051 y A. P. I. index 533 100 F. 210 F. Y

Original oil 20.7 2773 126 59.4 1070 Rafinate 24.9 1551 101.9 78.9 283 61 These data clearly demonstrate the excellent color removing power of our new admixture of solvents.

When three volumes of di(2-chlorethyl) ether, a representative widely used single-type solvent, were used at F. to extract one volume of dewaxed Mid-Continent S. A. E. 50 distillate having a viscosity of 114 seconds at 210 F., viscosity index of 56.5, true color of 1100 and a gravity of 21.6 A. P. I., a raffinate fraction was obtained which had a true color of 550. By comparing these data with those set forth in the above tables, it is apparent that our combinations of solvents are particularly effective in extracting the color bodies from mineral lubricating oils.

Similarly, an admixture of phenol and chloraniline have thepropcrty of producing a rafl'inate fraction having a high viscosity index and a low true color.

It is apparent that many modifications of the hereinbeiore described process can be made without departing from the scope of our invention.

5 Our novel combination of solvents may be used in a continuous process or batch process for extracting oils. These processes are described in our co-pending application 637,978 filed October 15, 1932 and our co-pending application 718,586 filed April 2, 1934. The present application is a continuation-in-part of these two co-pending applications.

We claim:

1. In a process for producing lubricating oil having a high viscosity index and a low true color from a mineral oil containing napthenic and parafiinic constituents, the steps comprising extracting the mineral oil with an admixture of solvents selected from the group consisting of to 40% chloraniline and 40 to 60% cresylic acid, to 40% chloraniline and 15 to 60% of phenol, 60 to 40% of chlorophenol and 40 to 60% of cresylic acid, to form two liquid layers, separating said layers and removing the solvents from each of the layers.

2. In a process for producing lubricating oil having a high viscosity index and a low true color from a mineral oil containing naphthenic and parafiinic constituents, the steps comprising extracting the mineral oil with an admixture of solvents selected from the group consisting of 15 to 85% cresylic acid and 85 to 15% of chloraniline, 15 to 85% cresylic acid and 85 to 15% of chlorophenol, and 15 to 60% of phenol and 85 to 40% of chloraniline, to form liquid layers, separating said layers and removing the solvents from each of the layers.

3. In a process for producing lubricating oil having a high viscosity index and a true color of less than 300 from a mineral oil containing naphthenic and paraffinic constituents and having a true color of more than 800, the steps comprising extracting the mineral oil with an admixture of solvents selected from the group consisting of 15 to 85% cresylic acid and 85 to 15% chloraniline, 15 to 85% cresylic acid and 85 to 15% chlorophenol, and 15 to 60% phenol and 85 to 40% chloraniline, to form two liquid layers, separating said layers and removing the solvents from each of the layers. I ARTHUR B. BROWN. FRED F. DIWOKY. 

